Vojany Black Coal Power Plant

Thermal power plant Vojany is situated in the Eastern Slovakia, district Michalovce. The installed generation capacity of currently operated units of the plant Vojany I (EVO I) is 2 x 110 MW. The advantageous location in the proximity of the Slovak-Ukrainian border, the utmost shortening of the semi-anthracite coal wide-gauge track from the Donbas-Kusbeck mining area and the possibility of cooling water off-take from the Laborec river were the most important considerations leading to the decision to build this thermal power plant.

By supplying base power the Vojany power plant ensures reliability of the transmission network in Eastern Slovakia and also provides ancillary services for the power system, necessary to sustain the stability of the system qualitative indicators. This is possible due to the wide output power range of units 5 and 6 from 40 or 50 MW respectively to 110 MW.

Since 2009, biomass (wooden chips) is co-fired with coal, contributing to the environment protection of the region and reducing substantially carbon dioxide emissions, while receiving no subsidies, e.g. guaranteed purchase price for the use of renewable energy. The share of biomass is 7 % (80 – 90 tons daily) at Unit 6, and as much as 22% at Unit 5, which is around 400 tons of biomass a day. During the years 2009 – 2015 the plant saved the environment of more than 220 000 tons of CO2 emissions.

The fuel for EVO I is the black anthracite coal with heating capacity of 25 GJ . t-1 imported from the Russian Federation, using the broad-gauge railway connected to the railway siding. After the completion of the 1st phase of the biomass co-firing project, since 2009 the fuel basis includes also wood chips. EVO II plant is off-line. It used natural gas and mazut.

In November 1959, the Headquarters of Power Plants Under Construction elaborated the original investment project - construction of a power plant with capacity 4x110 MW – and it was approved by the former Ministry of Power Engineering and Water Management in 1960. Lack of electricity in the developing economy of Czechoslovakia at the end of 50‘s was a basis for the Ministry of Power Engineering and Fuels to increase the installed capacity of the power plant up to 6x110 MW. The general designer of the construction was Energoprojekt Praha Company. Erecting the technological part was provided by ŠKODA Plzeň (in Pilsen) – supplying branch in Prague and construction works were done by Chemkostav Humenné Company in cooperation with dozens of other companies.

Construction of the Vojany Power Plant took place in 1961 – 1966. The individual units of the power plant were commissioned into operation in 1965 – 1966.

Power engineering balance of Czechoslovakia did not improve even in the beginning of 60's and the country step by step increased its dependency on energy import. In relation to the development of the fuel basis concept, the top priority became completing the missing power generating plants. Good conditions for construction of the Power plant Vojany II were provided by EVO I, the already completed broadgauge railway siding, and sufficient water resources which were supported by construction of water reservoir Zemplínska šírava. The design was based on the design of EVO I using original fuel sources. Due to the fact that the soviet counterpart pointed out to the fact that EVO II cannot be supplied with black anthracite coal, the fuel basis of EVO II was changed to heavy fuel oil during the construction. Due to the change of the fuel basis building a distillation unit called Slovnaft, unit Vojany was required.

Investment into Power Plant Vojany II was approved on 31 December 1966. Its construction started in 1968 and the individual units were commissioned in 1973 – 1974. The plant reached full installed capacity of 660 MW on 3 September 1974 by putting the unit No. 6 into trial run. After the crisis of energy industry in 1978 the supply of heavy fuel oil was limited and units at EVO II were reconstructed for combustion of natural gas.

At the end of ‘80s complex extended overhaul was performed on units 1 and 2 that included the replacement of mechanical precipitators with electrostatic ones and turbine generators modernization.

In 1997 an extended program for reconstruction and restoration started at Vojany. Through the above mentioned program in 1997 – 2001 desulphurisation and denitrification on EVO I units No. 1 and 2 and restoration of EVO I units No. 5 and 6 – replacement of classic combustion technology with combustion in fluid circulating layer were carried out. In 1997 – 2000 units No. 1 – 4  EVO II were reconstructed by replacement of burners with low-emission ones (Low-NOx).

In 2015 the regulatory range of units was extended to the power of 40 – 110 MW and the start-up time was significantly reduced. A test of biodegradable waste co-burning has been successfully performed. It proved that it was possible to co-fire a mixture of waste sludge, biomass and coal, and at the same time to provide ancillary services with the trend of 1,5 MW/min. The calorific ratio of biodegradable waste v.s. coal is 36 v.s. 64 %, the weight ratio is 61 v.s. 39 %.

The black-out start test is one of the most recent projects done in 2015 – 2016. To provide the service „black-out start“ the power plant has to meet certain technical requirements. In case of complete power system black-out, the power plant operates in a mode of a so-called „island“ created by the transmission and distribution grid operators. The other parts of the grid are gradually connected to this „island“ up to the complete electricity supply restoration. Units No. 5 and 6 are already prepared for this test.

Vojany I
EVO I installed capacity: 220 MW
Number of units: 2
Fuel: black semi-anthracite coal (T-coal)
Boilers 5 and 6: single-drum with natural circulation and circulating fluidised bed
Capacity: 325,4 t/hod
Output steam pressure: 14,6 Mpa
Construction commencement: 1997
Commissioned: 2001